Laser treatment of vascular abnormalities, such as portwine stain lesions (PWS), target the abnormally large PWS vessels with thermal damage, which yields clot formation in the PWS that elicits a wound healing response that removes the PWS. This treatment has been especially justified in children whose PWS are easily treated and provide a lifetime of normal appearance. However, there are often regions of treatment failure that require repeated treatments. Our working hypothesis is that treatment failure occurs because the treatment fails to induce a clot or the treatment-induced blood clot loosens and local blood flow is re-established thereby rescuing the PWS from the wound healing response. We propose a spectral camera system that can image the blood content and mixed arterio-venous oxygen saturation of the PWS before, immediately after, at 30 min, and at the 6-week follow-up exam, after laser treatment and indicate regions where blood perfusion has re-established. The acute measurements can predict regions of treatment failure and the measurements at follow-up can quantify the efficacy of treatments. No alteration of standard care will be done. The significance of the study is that once the correlation between reperfusion and treatment failure is demonstrated, justification would be established for immediate re-treatment of regions predicted to fail or other strategies for improving the stability of blood clots formed in the PWS by the procedure. The aims of this proposal are to (1) construct a prototype spectral camera for a pilot clinical study, (2) develop the analysis software that can efficiently analyze these images, and (3) conduct a pilot clinical study to establish the predictive value of the optical imaging. [unreadable] [unreadable] [unreadable]